The present invention relates to a rotary hydraulic machine for a hybrid automotive vehicle, as well as a hybrid vehicle equipped with such a hydraulic machine.
A known type of hydraulic cylinder machine, shown in particular in U.S. Pat. No. 5,358,338, comprises, on the side conventionally called the front side, a motorized input shaft which rotates a barrel having a succession of parallel or slightly inclined cylinders, distributed around the axis of this shaft. Each cylinder receives a piston axially resting on the front side on an inclined plate, which is fixed in rotation around the shaft of the machine by means of a bearing forming an axial lug. The incline of this plate along an axis perpendicular to the shaft of the hydraulic machine can be fixed or variable in order to change the piston displacement of the hydraulic machine.
One rotation of the barrel gives each piston a movement in a complete cycle, comprising one stroke depending on the angle of incline of the plate, which is adjustable by an incline control. The rear face of the barrel, opposite the inclined plate, is supported on a fixed circular top plate closing the end of the cylinders, held by a cover, which includes low and high pressure manifolds.
These machines generally can be operated by a motor or pump. Alternatively, the piston displacement may be fixed, with an incline angle from the top plate which is constant.
During the operation of this type of machine, sudden variations in pressure in the cylinders are obtained, as well as flexings of various components due to periodic stresses exerted on the machine, which generate vibrations at frequencies related to the number of pistons and the rotational speed of the shaft, which are transmitted to the outer casing of this machine.
These rotating machines usually comprise a casing, forming a body containing the cylinders, having a front transverse surface for supporting and fixing the machine to a support, and a rear transverse surface for receiving the top plate which comprises the fluid manifolds.
In order to fasten these hydraulic machines to the support, it is known to form a flange, on the transverse front support, which comprises a balance centered on the shaft, and around which a number of transverse mounting lugs project laterally from the body of the casing, each lug comprising one axial bore. There are generally two, three or four lugs axially presenting a low height of between 10 and 20 mm.
The support receiving the rotary hydraulic machine comprises bores, each receiving a threaded screw in a bore of the casing lug, which is tightened by the screw head or by a nut coming to rest behind this lug. This type of mounting is sized to achieve a mechanical strength, and a fatigue resistance over the life of the machine.
The casing of the machine equipped with this type of fastening comprises unique modes of vibration which can be activated by the different pulses during the operation of the rotating machine. One problem that arises is that it is possible to obtain, depending on the rotational speed and the hydraulic pressure, screeching noises emitted by these modes of vibration.
In particular, this type of rotary hydraulic machine, generally designed for industrial applications with an acceptable sound level for this field, may be unsuitable for use in a hydraulic hybrid automotive vehicle where noise constraints are important to ensure the comfort of passengers.
In addition, various known methods make it possible to reduce the excitation levels of these hydraulic machines, including, for example, special forms of opening of the manifolds on the mounted circular top plate, as presented in the document cited above. However, these solutions increase the costs of the machines.